We have used an old Jansport for a stove/ utility pack a couple times like you mentioned, and I would say it's tough enough. Last year I tried to get most things in the large packs but still brought it along for a daypack.

I'm not sure if they make it anymore, but check out the heritage series to get the basic idea. Mine didn't come pre-weathered.

There is also a inexpensive pack at campmor called the right pack that might work for you.